Gut–Brain Axis, Leaky Gut & Intestinal Permeability: The Complete Guide to Gut Health, Inflammation & Wellbeing
Gut–Brain Axis, Leaky Gut & Intestinal Permeability: The Complete Guide to Gut Health, Inflammation & Wellbeing
Interest in gut health has exploded in recent years—and for good reason.
Scientists now understand that the digestive system is far more than a place where food is broken down and nutrients are absorbed.
Your gut plays a central role in:
✔ Digestion and nutrient absorption
✔ Immune function
✔ Inflammation regulation
✔ Metabolic health
✔ Brain function and mood
✔ Healthy ageing
At the centre of these connections sits the gut–brain axis—a sophisticated communication network linking the digestive system, microbiome, immune system and brain.
Understanding how these systems interact can help explain why digestive symptoms often occur alongside issues such as fatigue, brain fog, poor concentration, skin concerns and inflammation.
This guide explores:
- The gut–brain axis
- Intestinal permeability ("leaky gut")
- The microbiome
- Gut dysbiosis
- Inflammation
- Akkermansia
- Probiotics
- Functional proteins
- Practical nutrition strategies for digestive wellbeing
Related:
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What Is Gut Health?
Gut health refers to the function and balance of the digestive system.
This includes:
- Digestion
- Nutrient absorption
- Gut barrier function
- Immune activity
- Microbiome diversity
- Communication with other body systems
A healthy digestive system helps regulate what enters the bloodstream while supporting nutrient absorption and overall wellbeing.
Modern research shows that gut health influences far more than digestion alone.
Related:
Building a Healthy Gut: Why Diversity Matters More Than Any 'Superfood'
Building a Healthy Gut: Why Diversity Matters More Than Any 'Superfood'
Gut Barrier Function: Your Body's First Line of Defence
The digestive tract does far more than digest food. It also acts as one of the body's most important protective barriers.
The intestinal lining forms a carefully regulated interface between the outside world and the internal environment of the body. Every day, it must allow nutrients, water and beneficial compounds to pass through while helping prevent unwanted substances from entering circulation.
This protective system is often referred to as the gut barrier.
The gut barrier consists of several interconnected layers including:
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The gut microbiome
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The mucus layer
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Intestinal epithelial cells
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Tight junctions between cells
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Gut-associated immune tissue
Together, these layers help maintain digestive health, support immune function and regulate communication between the gut and the rest of the body.
The Role of Tight Junctions
The intestinal lining is made up of specialised cells connected by structures known as tight junctions.
These tight junctions act like gatekeepers, helping regulate what moves from the digestive tract into the bloodstream.
When functioning normally:
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Nutrients can be absorbed efficiently
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Water and minerals can pass through
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Larger unwanted substances are restricted
Researchers now understand that these junctions are dynamic and respond to factors such as diet, stress, inflammation, medications, exercise and changes within the gut microbiome.
Why Gut Barrier Health Matters
Maintaining a healthy gut barrier is important for overall wellbeing.
Researchers continue to investigate how changes in intestinal permeability may influence:
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Digestive health
-
Immune function
-
Inflammatory processes
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Metabolic health
-
Gut–brain communication
Because the gut, immune system and nervous system are closely connected, supporting gut barrier function has become an important area of modern health research.
Related:
Zonulin, Gut Barrier Function & Intestinal Permeability Explained
Supporting a Healthy Gut Barrier
A healthy gut barrier is supported by a combination of lifestyle and dietary factors, including:
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Eating a diverse range of whole foods
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Consuming adequate protein
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Increasing fibre-rich plant foods
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Supporting microbiome diversity
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Managing stress
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Prioritising sleep
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Limiting ultra-processed foods
Bone broth is often included as part of a food-first approach because it contains collagen-derived amino acids including glycine, proline and glutamine, which contribute to overall nutrition and digestive wellbeing.
Rather than focusing on a single nutrient or supplement, the goal is to support the entire gut ecosystem—from the microbiome and gut lining to the immune system and gut–brain axis.
The Gut–Brain Axis Explained
The gut and brain communicate continuously through a network known as the gut–brain axis.
Communication occurs through:
The Vagus Nerve
A direct communication pathway between the digestive tract and brain.
The Immune System
Much of the body's immune activity occurs within the digestive tract.
Hormonal Signalling
The gut produces hormones involved in appetite, satiety and energy regulation.
The Microbiome
Gut bacteria produce compounds that interact with multiple body systems.
Together these systems create a constant two-way flow of information.
This helps explain why stress can affect digestion and why digestive issues can sometimes influence mood, concentration and wellbeing.
Gut Health, Mood & Mental Wellbeing
The connection between the gut and brain extends beyond digestion.
Researchers now recognise that the gut and brain communicate continuously through the gut–brain axis, influencing mood, stress responses and overall wellbeing.
The gut microbiome helps produce and regulate compounds involved in communication between the digestive system, immune system and brain. Because of this connection, poor digestive health is often associated with symptoms such as:
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Brain fog
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Fatigue
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Difficulty concentrating
-
Low mood
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Increased stress sensitivity
While gut health is not the sole cause of mental health concerns, supporting digestive wellbeing through whole foods, adequate sleep, movement and stress management may contribute to overall wellbeing.
A healthy gut supports a healthy foundation for both physical and mental resilience.
Related:
Nutrition for Stress Resilience: 10 Foods That Support Mood, Focus & Nervous System Health
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Gut Health, Immune Function & Autoimmune Conditions
Approximately 70% of the body's immune cells are located within or around the digestive tract, highlighting the close relationship between gut health and immune function.
The gut barrier and microbiome help regulate how the immune system responds to the outside world. When the digestive system is functioning well, it supports healthy immune regulation and resilience.
Researchers continue to investigate the relationship between intestinal permeability, the microbiome and autoimmune conditions. While autoimmune diseases are complex and influenced by many factors, maintaining a healthy gut environment may play an important role in supporting overall immune balance.
Practical strategies include:
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Eating a diverse range of whole foods
-
Increasing fibre intake
-
Supporting microbiome diversity
-
Prioritising sleep
-
Managing stress
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Including nutrient-dense foods such as bone broth, vegetables and quality protein as part of a balanced diet
Supporting gut health is not a treatment for autoimmune conditions, but it may contribute to overall wellbeing and healthy immune function.
Deep Dive:
The Gut-Brain-Immune Connection: How Your Gut Influences Whole-Body Health
Your Microbiome: The Ecosystem Within
The microbiome refers to the trillions of microorganisms that live primarily within the large intestine.
These microbes influence:
- Digestion
- Nutrient metabolism
- Immune regulation
- Gut barrier integrity
- Inflammatory balance
A diverse microbiome is generally associated with better digestive resilience and overall health.
The majority of probiotics live within the colon (large intestine), where they help maintain this complex ecosystem.
What Is Intestinal Permeability?
The digestive tract contains a protective barrier made up of specialised cells connected by structures called tight junctions.
These tight junctions regulate what passes from the digestive tract into circulation.
Researchers use the term intestinal permeability to describe how substances move across this barrier.
When permeability increases, the barrier may become less selective.
This process is commonly referred to as leaky gut.
Although "leaky gut" is not a formal medical diagnosis, intestinal permeability is an active area of scientific investigation.
Why the Gut Barrier Matters
The gut barrier performs several important functions.
It helps:
- Absorb nutrients
- Prevent unwanted substances from crossing into circulation
- Support immune regulation
- Maintain digestive resilience
Researchers continue to investigate how changes in gut barrier function may influence digestive wellbeing, immune activity and broader health outcomes.
The Broth & Co Gut Health Study
In 2021, Broth & Co conducted an eight-week gut health study investigating daily bone broth consumption.
The study observed improvements in the mannitol:inositol ratio, a marker associated with intestinal permeability and gut barrier function.
Participants also reported improvements in digestive wellbeing, including reductions in bloating and food sensitivities.
While additional research is always valuable and individual responses may vary, the findings contribute to growing interest in nutrient-dense whole foods as part of healthy dietary patterns.
What Is Gut Dysbiosis?
Gut dysbiosis refers to an imbalance in the microbiome.
Potential contributors include:
- Ultra-processed foods
- Low fibre intake
- Chronic stress
- Poor sleep
- Antibiotic use
- Reduced dietary diversity
Signs commonly associated with digestive imbalance may include:
- Bloating
- Digestive discomfort
- Irregular bowel habits
- Fatigue
- Brain fog
- Reduced resilience
Read More:
Akkermansia: One of the Most Researched Gut Bacteria
One of the most exciting areas of microbiome research involves a bacterium called Akkermansia muciniphila.
Researchers are interested in Akkermansia because of its association with:
- Gut barrier integrity
- Metabolic health
- Blood sugar regulation
- Healthy ageing
- Inflammatory balance
Ways to support Akkermansia include:
- Increasing plant diversity
- Eating polyphenol-rich foods
- Reducing ultra-processed foods
- Supporting gut barrier health
Why Probiotics Don't Always Work
Many people assume probiotics are the first solution for gut issues.
However, probiotics are only one piece of the puzzle.
Think of the digestive system like a garden:
- The gut lining = soil
- Fibre = fertiliser
- Probiotics = seeds
If the environment is unhealthy, beneficial bacteria may struggle to thrive.
This is why many people experience:
- Minimal improvement
- Temporary benefits
- Symptoms returning after stopping supplements
The goal is to support the entire gut environment.
Read More:
Leaky Gut, Intestinal Permeability & Gut Barrier Function: The Complete Guide
The Gut–Inflammation Connection
The digestive system and immune system are closely linked.
When digestive function becomes compromised:
- Immune activity may increase
- Inflammatory signalling may rise
- Recovery and resilience may decline
Researchers continue to explore how digestive health may influence broader inflammatory processes throughout the body.
Read More:
Chronic Inflammation Explained: Diet, Lifestyle, Gut Health & Everyday Wellbeing
Functional Proteins & Gut Health
Protein is essential for:
- Tissue maintenance
- Muscle repair
- Healthy ageing
- Recovery
Bone broth and collagen peptides are often referred to as functional proteins because they provide collagen-derived amino acids including:
- Glycine
- Proline
- Glutamine
At Broth & Co, both bone broth and BC Beauty collagen peptides contribute approximately 5g of protein per serve.
Many people include these products within balanced dietary patterns focused on wellbeing and healthy ageing.
Read More:
Where Bone Broth Fits Into a Gut Health Routine
Bone broth has been used traditionally across cultures for generations.
Many people enjoy it:
Morning
As a warming start to the day.
Between Meals
As a nourishing savoury snack.
In Cooking
As a base for:
- Soups
- Stews
- Sauces
- Risottos
- Slow-cooked meals
Bone broth works best when incorporated into a healthy dietary pattern that includes vegetables, fruit, fibre-rich foods and quality protein sources.
Learn More:
Healing Soups & Nourishing Broths: Bone Broth Recipes for Recovery
Practical Strategies to Support Gut Health
1. Prioritise Whole Foods
Focus on:
- Vegetables
- Fruit
- Quality protein
- Nuts and seeds
- Legumes where tolerated
2. Increase Fibre Intake
Fibre helps support:
- Regular digestion
- Microbiome diversity
- Satiety
3. Include Fermented Foods
Examples include:
- Natural yoghurt
- Kefir
- Sauerkraut
- Kimchi
- Miso
4. Stay Hydrated
Hydration supports digestive function and overall wellbeing.
5. Prioritise Sleep
Sleep influences:
- Recovery
- Appetite regulation
- Stress responses
- Microbiome balance
6. Move Regularly
Walking, resistance training and general movement support overall health.
7. Manage Stress
The gut–brain axis is highly responsive to stress.
Strategies include:
- Walking
- Breathing exercises
- Time outdoors
- Mindfulness practices
Building a Sustainable Gut Health System
Long-term health rarely comes from extreme interventions.
Focus on daily habits:
✓ Whole foods
✓ Fibre
✓ Quality protein
✓ Hydration
✓ Sleep
✓ Movement
✓ Stress management
✓ Consistency
Small actions repeated over time create the strongest foundation for digestive wellbeing.
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